Charge Transfer through DNA: A Selective Electrochemical DNA Biosensor

The charge-transfer properties of DNA duplexes are exploited to produce a fast, simple, sensitive, and selective DNA biosensor by exposing the DNA recognition interface to a sample containing target DNA and the redox-active intercalator, anthraquinonemonosulfonic acid (AQMS). Electrochemistry from electron transfer through the DNA to AQMS intercalated into DNA duplexes can be differentiated from electrochemistry due to direct access of the AQMS to the electrode surface due to the difference in the environment of the AQMS giving a shift in the potential at which the molecule is reduced. The ability to distinguish between the two electrochemical signals enables DNA hybridization to be monitored in real time. This in situ detection scheme has good selectivity, being able to differentiate between a complementary target DNA sequence and one containing either C−A or G−A single-base mismatches. The concentration detection limit of the biosensor is 0.5 nM (1 pmol) with an assay time of 1 h. The fact that the end user is only required to simultaneously add the sample containing the target DNA and AQMS gives a DNA biosensor that is highly compatible with PCR on chip technologies.